Burner tube assemblies, including those used in gas grills, are common in the art. A typical configuration of a burner assembly may be seen generally in FIG. 1A (see also U.S. Pat. No. 6,102,029, assigned to Weber-Stephen Products LLC). As shown, such an assembly typically includes a plurality of elongated hollow burner tubes 1, each burner tube 1 having a closed end 2, an open or inlet end 3, as well as a venturi region 4. A plurality of gas ports 5 are provided along the length of the burner tube 1. The open end 3 of burner tube 1 may be provided with a cut-out section 6 that aids in the introduction of combustion air into the burner tube 1.
To distribute the fuel to be burned to the burner tubes 1, a gas distribution manifold 7 is provided. A plurality of gas control valves 8 to selectively control the amount of fuel delivered to the burner tubes 1 are in fluid communication with the manifold 7 and with each burner tube 1 through a valve including a valve neck 9. The valve neck 9 includes a nozzle 18 at its end (not shown in FIG. 1A) to inject the gas into the open end 3 of burner tubes 1. The majority of the burner tube assembly, and particularly that portion rearward of valve neck 9, is located within the fire box of the gas grill. As a result, the burner tubes are subject to wide temperature fluctuations and the expansion and contraction of the burner tubes must be accommodated, as discussed below.
An air shutter 10 is also included on each burner tube 1 in a typical burner tube assembly. A typical sleeve-type air shutter 10, valve neck 9 and burner tube 1 are also shown in FIG. 1B (see also U.S. Pat. No. 4,416,249). Air shutter 10 includes a face 11 having an opening 12, the shape of which coincides with the cross-sectional shape of valve neck 9. Similarly, the shape of the air shutter 10 generally coincides with the shape of the open end 3 of burner tube 1. Air shutter 10 also includes a rearwardly projecting sleeve or skirt 13, typically including at least one aperture or window 14. The skirt 13 of air shutter 10 is slip fit over the open end 3 of burner tube 1. In this manner, air shutter 10 may be rotated around the open end 3 of burner tube 1 such that an air gap 15 (see FIG. 1A) may be created by varying the alignment of window 14 on the air shutter 10 with the cut-out section 6 of the open end 3 of burner tube 1. The amount of ah mixed with gas may thus be adjusted.
As shown in FIGS. 1B and 1C, the central opening 12 on the face 11 of air shutter 10 receives the valve neck 9 and is supported thereby. Control valve 8 and valve neck 9 are rigidly secured to the grill and/or grill frame assembly (not shown). Because the burner tube 1 expands and contracts during heating and cooling, air shutter 10 is not rigidly secured to valve neck 9, which simply protrudes through the central opening 12 and supports the air shutter 10 and thus, burner tube 1. The closed end 2 of burner tube 1 is also typically movably attached to a bracket or other portion of the fire box at the rear of a grill. As a result, the burner tube 1 is able to expand and contract during use without damage to it, the valve or other grill components.
While such a typical configuration is satisfactory for many purposes, there are certain drawbacks. For example, and as best shown in FIG. 1C, because of the loose fit between the valve neck 9 and the central opening 12 of the air shutter, there is typically only one point or area of contact 19 between the two components. This limited point of contact 19 can negatively impact the operation of a typical ignition system or igniter 40, especially if there is debris, corrosion or the like between the valve neck 9 and central opening 12. In addition, and for similar reasons, the nozzle 18 at the end of the valve sleeve 9 is not centrally aligned with the interior center of the burner tube 1, also as shown in FIGS. 1B and 1C. This can result in decreased efficiency of fuel usage and impact the quality of the resultant flame.